In the cigarette making art, small particles of tobacco and tobacco fines resulting from the handling of tobacco leaf and the manufacture of cigarettes and other tobacco products are recycled into a web or sheet product known as reconstituted tobacco, for example, by conventional paper making processes. The webs or sheets are then cut into smaller pieces then shredded into strips useful as cut filler in the cigarette making process. Similarly, in other arts, such as plastic molding, a web of plastic sheet material may be cut into smaller pieces or chips for subsequent processing.
Typically, if the web to be cut into smaller pieces has a width greater than the desired dimensions of the final cut product, the web is slit longitudinally in the direction of travel of the web with one or more knives or cutters and is then cut transversely to the direction of travel. Alternatively, the web may be initially cut transversely across the web width to form elongated strips which are then cut into two or more strips of shorter lengths.
European Patent Publication No. 0124255 discloses one known apparatus and method of the former type for shredding a sheet material in which a longitudinally pre-slit web of reconstituted tobacco or blended leaf tobacco is fed off the end of a support table past a serrated ledger blade supported at the edge of the table. A complementary serrated blade fixed to a rotating cylinder strikes the projecting sheet portion extending past the ledger blade, penetrates the sheet and separates the projecting portion of the sheet by tearing. According to this cutter design, a clearance is maintained between the fixed ledger blade and the moving blade so that there is no interference between the blades. The absence of interference is said to be advantageous to solve the problems of blade wear, noise and blade adjustment owing to sagging of the rotating shaft of the cutter. Because the sheet material is longitudinally pre-slit, the transverse cutting or tearing of the projecting portion results in a cut product having a length equal to the spacing between the pre-slits and a width proportional to cutter speed and the feed rate of the sheet, i.e., equal to the distance the web of sheet material is advanced between successive cuts or tears by the moving blade or blades.
U.S. Pat. No. 2,335,515 to Jehle discloses a cutting method and apparatus with a fixed and a movable cutter which is used to cut a sheet of plastic material into small pieces or chips suitable for a plastic molding process. According to this patent, the movable cutter is made up of a plurality of toothed cutters arranged axially on a rotating shaft in two sets with the cutters of the first set alternating with the cutters of the second set and the teeth of the first set being circumferentially offset or staggered with the teeth of the second set. With this arrangement, rotation of the movable cutter and advancement of the sheet will cause one row of the first set of teeth to cut pieces from the sheet having a length equal to the transverse width of the teeth of the first set, then one row of the second set of teeth to cut pieces from the sheet having a length equal to the transverse width of the teeth of the second set, then the second row of the first set of teeth to cut pieces from the sheet and so on. Thus, each set of cutter teeth cuts alternate pieces from the sheet so that two rows of cutter teeth must cut the sheet to cut off pieces equal in length to one entire sheet width.
It would be desirable to provide a sheet cutting apparatus and method having a movable cutter blade that is capable of coacting with a fixed cutter blade to substantially simultaneously cut the entire width of a web of sheet material both longitudinally as well as transversely into cut pieces of desired dimensions so that pre-slitting of the sheet is unnecessary. It would also be desirable to provide a cutting apparatus having blades that are substantially self-sharpening and are characterized by substantially reduced blade wear.